This present application relates to a preparation process of microbeads and also to microbeads. More specifically, the present application is concerned with a process for preparing microbeads with a predetermined substance immobilized on their surfaces by conducting photolithography on a substrate and also with the microbeads so prepared.
In a biochemical analysis for a nucleic acid, protein or the like, a particulate carrier called “microbeads” has been used in related art. In a nucleic acid analysis, for example, microbeads with probe nucleic acid chains, which have a complementary base sequence to target nucleic acid chains, immobilized thereon are used, and the target nucleic acid chains are isolated based on an interaction between the target nucleic acid chains and the probe nucleic acid chains. In a protein analysis, on the other hand, a target protein is similarly isolated using microbeads on surfaces of which an antibody to the target protein is immobilized.
Concerning biochemical analyses making use of these microbeads, there is an outstanding demand in recent years toward still higher throughputs, resulting in the increasing development of technologies for achieving the speed-up of analyses.
For example, Japanese Patent No. 3468750 (hereinafter referred to as Patent Document 1) discloses: “A method of detecting a plurality of analytes in a sample, each of said analytes being recognized by a respective analytical reactant, including: a) contacting the sample with a plurality of populations of fluorescent particles, each population of said particles having a distinct fluorescent signal and a distinct analytical reactant, wherein said analytical reactant specifically binds one of the analytes in said sample, each fluorescent particle including at least one nanoparticles labeled with a respective fluorescent dye; b) adding the sample to a label reagent; c) analyzing the particles to detect said label, which indicates the binding of the analyte to the analytical reactant; and simultaneously, d) determining the populations of particles having bound the respective analyte as a function of the distinct fluorescent signal associated with each said population” (see claim 23).
With the “Suspension Array Technology” furnished by Luminex Corporation on the basis of the above-described technology, it is possible to identify a maximum of as many as 100 types of microbeads by labeling the microbeads with two kinds of fluorescent dyes (hereinafter referred to as “fluorochromes”) while providing variations in the color of emission. According to the “Suspension Array Technology,” 100 kinds of different nucleic acid chains or proteins can be isolated and detected at the same time in a single analysis by immobilizing different probe nucleic chains or antibodies on 100 sets of microbeads, respectively.
Patent Document 1 in the above also describes: “said populations of fluorescent particles are further determined according to their size or shape” (see claim 25). This patent publication also discloses to the effect that the size or shape of the particle can be adopted as an additional distinction parameter (see paragraph [0037], etc.). In connection with the foregoing, a method for preparing a multiplicity of sets of microbeads of different shapes by photolithography in a microfluidic channel is described in “Multifunctional Encoded Particles for High-Throughput Biomolecule Analysis,” Science, 315(5817), 1393-6 (9 Mar. 2007) (hereinafter referred to as Unexamined Document 1). According to this method, over a million sets of microbeads can be prepared.